This shared instrumentation grant proposes to purchase an IVIS Spectrum In vivo Imaging System. The IVIS spectrum is a powerful and versatile research tool that permits optical imaging of both bioluminescent and fluorescent signals over a wide range of emission and excitation frequencies in small research animals. The instrument is equipped with 10 excitation filters (30 nm bandwidth) and 18 emission filters (20 nm bandwidth) for transmission and reflectance-mode fluorescence imaging in vivo with additional capacity to perform quantitative 3D tomography. Sophisticated and powerful software allows for absolute quantification of signal, a feature critical for comparing samples within and between different experiments. Combined with images obtained from a super cooled CCD camera, the software also provides critical spectral unmixing features that allow for highly sensitive signal to noise discrimination and resolution. Highly skilled staff of the Immune Disease Institute's Flow Cytometry Core facility will oversee operations, management and maintenance of this instrument. This application is a joint proposal from the leading immunology research institute at Harvard Medical School, the Immune Disease Institute (IDI) and Program in Cellular & Molecular Medicine (PCMM) at Children's Hospital Boston. In addition to the 7 core investigators listed on this proposal, the instrument will also be made available to all investigators that maintain animals in Harvard Medical School Animal Facility at 200 Longwood Avenue in Boston where the machine will be located. It is noteworthy that this animal facility does not have an in vivo imaging system. Currently there are 59 investigators maintaining animals in this facility with affiliations to the Harvard Medical School, Children's Hospital Bosto, and Brigham and Women's Hospital Boston. Thus the IVIS Spectrum in vivo imaging system will be a major resource for the Harvard Medical School community in addition to the core users whose proposed research is detailed in this grant. The requested instrumentation will provide these researchers with the capacity for whole body bioluminescent and fluorescent imaging of laboratory animals, a technology that will allow them to answer important questions in a broad diversity of fields including immunology, stem cell biology, and disease pathogenesis. .